Description

The main idea behind this project is to refurbish LPKF Protomat C20 PCB milling machine with open source hardware, firmware and software.

The LPKF C20 machine is a PCB milling machine that creates a PCB board by milling the contour based from the PCB design. We bought this machine in 2005 and the machine has stop functioning due to faulty at controller board.

Since the machine is a close-sourced machine, the only way to repurpose the machine is to make use of the existing hardware and replacing the board controller.

Details

Overview of Machine

Front View

Power indicator
X-axis motor
DC Spindle Motor / Plotter
Working Depth Limiter

Rear View

Vacuum System Connection
Serial port (9-pin) for expansion units
Serial port (25-pin) for connection to PC
X Motor Connection
Y Motor Connection
Connection for plotter head
ON/OFF switch with mains connector and fuses
X Motor
Y Motor

Plotter Board

Normally Open Limit Switches for – Y axis
Common terminal for Limit Switches
Spindle / Plotter +DC Supply
Spindle / Plotter –DC Supply
Solenoid Actuator +DC Supply
Solenoid Actuator –DC Supply
NC
NC
NC
Normally Open Limit Switches for +Y Axis

Controller Board

Mains EMI Filter
Transformer
Rectifier (GBU4D) 34V DC Output
Rectifier (GBU4D) 78V DC Output
Rectifier (GBU4D) 11V Dc Output
Processing Unit
Stepper Motor Controller (L6203) DMOS Full Bridge Driver
Stepper Motor Controller (L6203) DMOS Full Bridge Driver
Plotter Head Controller

Plotter / Spindle Head

Shock Absorber
Solenoid
Working Depth Limiter
Tool Changer Handle
Mounting for Spindle
DC Spindle Motor
Vacuum Connector

Components

1 × Arduino MEGA

1 × RAMPS 1.4

2 × Allegro A4988 Stepper Motor Driver

1 × TIP125 Darlington Transistor

1 × PN2222 Transistor

Project Logs

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Build Instructions

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1

Replacing Controller Board

The controller board was replaced with Open Sourced CNC Machine controller board called RAMPS board or in this case RAMPS version 1.4. This board mainly consist of header for microcontroller, limit switches, stepper motor driver , input supply and with polyfuse to protect against overcurrent, mosfet to drive spindle output.

RAMPS 1.4 Overview

RAMPS 1.4 Schematic
2

Replacing Processing Unit

The processing unit was replace with Open Sourced microcontroller board based on ATmega 2560 chip. This microcontroller unit consist of power regulator, UART for USB interfaces, serial communications, and multiple GPIO for controller output.

Arduino MEGA Overview
3

Replacing Stepper Motor Driver

A Breakout board for Allegro’s A4988 was used to control the stepper motors. This board was specifically used to control bipolar stepper motor and features adjustable current limiting, overcurrent and over temperature protection and five different microstep resolutions. It is able to deliver up to 1A per phase without heat sink

Allegro A4988 Overview